On dotCommonweal someone commented
The question that occurs to me is that some things now considered “intrinsically evil,” such as slavery, can be recognized as evil at the time, if not by the perpetrators, at least by the victims. But it seems like other “intrinsic evils” (mainly those involving sexual behavior) are kind of like victimless crimes. And if the perpetrators don’t know they are evil — how can I put this? — where does the evil go? For example, suppose in the movie Blue Lagoon, the two youngsters that grew up on the island together had not been Brooke Shields and Christopher Atkins, but two males or two females who developed, in all innocence, a sexual relationship. They would not be guilty of doing anything wrong, and assuming it was a loving, caring relationship, no harm would come of it. So where there is no culpability and no negative outcome, what does it mean to say that objectively there was evil? Are some “intrinsic evils” kind of like “technical violations”?
“They would not be guilty of doing anything wrong.” What I find interesting in this comment is the underlying voluntarism: that harm is done only by disobeying a known law. That is, actions are wrong because God forbids them; God doesn’t forbid them because they are wrong in themselves. This error still pervades many Catholics’ approach to moral questions.